Curved laminates are used in a variety of applications including automotive glazing and architectural windows. For such applications, sheets of glass are precisely bent to defined shapes and/or curvatures determined by the configurations and sizes of the openings, as well as the vehicle style or architectural aesthetics. Such curved laminates may be made by heating flat glass sheets to a suitable temperature for forming, applying forces to the sheet to change the shape, then laminating two curved sheets together. This process is typically referred to as a “hot bending” process. In some known examples, the glass may be heated in a furnace and formed while the sheet is still in a high temperature state (at or near the softening temperature of the glass) within the furnace. Glass sheets may also be bent by initially heating the glass sheet in a furnace to a suitable temperature at or near the softening temperature of the glass, then transferring the glass sheet to a glass bending apparatus outside the furnace. Glass sheets that undergo such bending operations typically have been 2.5 mm, 3 mm, or greater in thickness.
Curved laminates typically must meet stringent optical requirements, and the viewing area of the closures or windows must be free of surface defects and optical distortion that can interfere with the clear viewing through the curved laminate. Glass that is not at an appropriate temperature during a bending operation may exhibit optical distortions, such as roller waves (optical roll distortion) and/or discrete marking(s) and/or defect(s) that may make the bent sheet unsuitable for its intended purpose.
Presently existing methods to form complexly curved laminates presently require heating and bending two glass sheets at or near the softening point of the glass to form a single laminate, and/or typically use very thick glass sheets to facilitate bending operations leading to greater overall weight of the laminate. Moreover, when two glass sheets require differing forming conditions or processes (e.g., due to differing softening points and/or thicknesses), the two glass sheets are typically formed separately and then joined, often leading to shape mismatch and unnecessary processing steps and cost. Accordingly, such methods require complex manufacturing processes incurring longer manufacturing time and more cost.
Automotive glazing and architectural applications are increasingly demanding complexly curved laminates, which are thinner than currently available laminates. Accordingly, there is a need for such laminates that can be shaped and laminated using fewer processing steps and having more precise shape matching.